Add c interface which wraps the cpp classes

include/axolotl/axolotl.hh

+#ifndef AXOLOTL_HH_
+#define AXOLOTL_HH_
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static const size_t AXOLOTL_MESSAGE_TYPE_PRE_KEY = 0;
+static const size_t AXOLOTL_MESSAGE_TYPE_MESSAGE = 1;
+
+struct AxolotlAccount;
+struct AxolotlSession;
+
+size_t axolotl_account_size();
+
+size_t axolotl_session_size();
+
+AxolotlAccount * axolotl_account(
+    void * memory
+);
+
+AxolotlSession * axolotl_session(
+    void * memory
+);
+
+size_t axolotl_error();
+
+const char * axolotl_account_last_error(
+    AxolotlSession * account
+);
+
+const char * axolotl_session_last_error(
+    AxolotlSession * session
+);
+
+size_t axolotl_pickle_account_length(
+    AxolotlAccount * account
+);
+
+size_t axolotl_pickle_session_length(
+    AxolotlSession * session
+);
+
+size_t axolotl_pickle_account(
+    AxolotlAccount * account,
+    void const * key, size_t key_length,
+    void * pickled, size_t pickled_length
+);
+
+size_t axolotl_pickle_session(
+    AxolotlSession * session,
+    void const * key, size_t key_length,
+    void * pickled, size_t pickled_length
+);
+
+size_t axolotl_unpickle_account(
+    AxolotlAccount * account,
+    void const * key, size_t key_length,
+    void * pickled, size_t pickled_length
+);
+
+size_t axolotl_unpickle_session(
+    AxolotlSession * session,
+    void const * key, size_t key_length,
+    void * pickled, size_t pickled_length
+);
+
+size_t axolotl_create_account_random_length(
+    AxolotlAccount * account
+);
+
+size_t axolotl_create_account(
+    AxolotlAccount * account,
+    void const * random, size_t random_length
+);
+
+size_t axolotl_account_identity_keys_length(
+    AxolotlAccount * account
+);
+
+size_t axolotl_account_identity_keys(
+    AxolotlAccount * account,
+    void * identity_keys, size_t identity_key_length
+);
+
+size_t axolotl_account_one_time_keys_length(
+    AxolotlAccount * account
+);
+
+size_t axolotl_account_one_time_keys(
+    AxolotlAccount * account,
+    void * identity_keys, size_t identity_key_length
+);
+
+/* TODO: Add methods for marking keys as used, generating new keys, and
+ * tracking which keys have been uploaded to the central servers */
+
+size_t axolotl_create_outbound_session_random_length(
+    AxolotlSession * session
+);
+
+size_t axolotl_create_outbound_session(
+    AxolotlSession * session,
+    AxolotlAccount * account,
+    void const * their_identity_key, size_t their_identity_key_length,
+    unsigned their_one_time_key_id,
+    void const * their_one_time_key, size_t their_one_time_key_length,
+    void const * random, size_t random_length
+);
+
+size_t axolotl_create_inbound_session(
+    AxolotlSession * session,
+    AxolotlAccount * account,
+    void * one_time_key_message, size_t message_length
+);
+
+size_t axolotl_matches_inbound_session(
+    AxolotlSession * session,
+    void * one_time_key_message, size_t message_length
+);
+
+size_t axolotl_encrypt_message_type(
+    AxolotlSession * session
+);
+
+size_t axolotl_encrypt_random_length(
+    AxolotlSession * session
+);
+
+size_t axolotl_encrypt_message_length(
+    AxolotlSession * session,
+    size_t plaintext_length
+);
+
+size_t axolotl_encrypt(
+    AxolotlSession * session,
+    void const * plaintext, size_t plaintext_length,
+    void const * random, size_t random_length,
+    void * message, size_t message_length
+);
+
+size_t axolotl_decrypt_max_plaintext_length(
+    AxolotlSession * session,
+    size_t message_type,
+    void * message, size_t message_length
+);
+
+size_t axolotl_decrypt(
+    AxolotlSession * session,
+    size_t message_type,
+    void * message, size_t message_length,
+    void * plaintext, size_t max_plaintext_length
+);
+
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* AXOLOTL_HH_ */

src/axolotl.cpp

+#include "axolotl/axolotl.hh"
+#include "axolotl/session.hh"
+#include "axolotl/account.hh"
+#include "axolotl/base64.hh"
+#include "axolotl/cipher.hh"
+
+#include <new>
+#include <cstring>
+
+namespace {
+
+static AxolotlAccount * to_c(axolotl::Account * account) {
+    return reinterpret_cast<AxolotlAccount *>(account);
+}
+
+static AxolotlSession * to_c(axolotl::Session * account) {
+    return reinterpret_cast<AxolotlSession *>(account);
+}
+
+static axolotl::Account * from_c(AxolotlAccount * account) {
+    return reinterpret_cast<axolotl::Account *>(account);
+}
+
+static axolotl::Session * from_c(AxolotlSession * account) {
+    return reinterpret_cast<axolotl::Session *>(account);
+}
+
+static std::uint8_t * from_c(void * bytes) {
+    return reinterpret_cast<std::uint8_t *>(bytes);
+}
+
+static std::uint8_t const * from_c(void const * bytes) {
+    return reinterpret_cast<std::uint8_t const *>(bytes);
+}
+
+static const std::uint8_t CIPHER_KDF_INFO[] = "Pickle";
+
+static const axolotl::CipherAesSha256 PICKLE_CIPHER(
+    CIPHER_KDF_INFO, sizeof(CIPHER_KDF_INFO) -1
+);
+
+std::size_t enc_output_length(
+    size_t raw_length
+) {
+    std::size_t length = PICKLE_CIPHER.encrypt_ciphertext_length(raw_length);
+    length += PICKLE_CIPHER.mac_length();
+    return axolotl::encode_base64_length(length);
+}
+
+
+std::uint8_t * enc_output_pos(
+    std::uint8_t * output,
+    size_t raw_length
+) {
+    std::size_t length = PICKLE_CIPHER.encrypt_ciphertext_length(raw_length);
+    length += PICKLE_CIPHER.mac_length();
+    return output + axolotl::encode_base64_length(length) - length;
+}
+
+std::size_t enc_output(
+    std::uint8_t const * key, std::size_t key_length,
+    std::uint8_t * output, size_t raw_length
+) {
+    std::size_t ciphertext_length = PICKLE_CIPHER.encrypt_ciphertext_length(
+        raw_length
+    );
+    std::size_t length = ciphertext_length + PICKLE_CIPHER.mac_length();
+    std::size_t base64_length = axolotl::encode_base64_length(length);
+    std::uint8_t * raw_output = output + base64_length - length;
+    length -= PICKLE_CIPHER.mac_length();
+    PICKLE_CIPHER.encrypt(
+        key, key_length,
+        raw_output, raw_length,
+        raw_output, ciphertext_length,
+        raw_output, length
+    );
+    axolotl::encode_base64(raw_output, length, output);
+    return raw_length;
+}
+
+std::size_t enc_input(
+    std::uint8_t const * key, std::size_t key_length,
+    std::uint8_t * input, size_t b64_length,
+    axolotl::ErrorCode & last_error
+) {
+    std::size_t enc_length = axolotl::decode_base64_length(b64_length);
+    if (enc_length == std::size_t(-1)) {
+        last_error = axolotl::ErrorCode::INVALID_BASE64;
+        return std::size_t(-1);
+    }
+    axolotl::decode_base64(input, b64_length, input);
+    std::size_t raw_length = enc_length - PICKLE_CIPHER.mac_length();
+    std::size_t result = PICKLE_CIPHER.decrypt(
+        key, key_length,
+        input, enc_length,
+        input, raw_length,
+        input, raw_length
+    );
+    if (result == std::size_t(-1)) {
+        last_error = axolotl::ErrorCode::BAD_ACCOUNT_KEY;
+    }
+    return result;
+}
+
+
+std::size_t b64_output_length(
+    size_t raw_length
+) {
+    return axolotl::encode_base64_length(raw_length);
+}
+
+std::uint8_t * b64_output_pos(
+    std::uint8_t * output,
+    size_t raw_length
+) {
+    return output + axolotl::encode_base64_length(raw_length) - raw_length;
+}
+
+std::size_t b64_output(
+    std::uint8_t * output, size_t raw_length
+) {
+    std::size_t base64_length = axolotl::encode_base64_length(raw_length);
+    std::uint8_t * raw_output = output + base64_length - raw_length;
+    axolotl::encode_base64(raw_output, raw_length, output);
+    return base64_length;
+}
+
+std::size_t b64_input(
+    std::uint8_t * input, size_t b64_length,
+    axolotl::ErrorCode & last_error
+) {
+    std::size_t raw_length = axolotl::decode_base64_length(b64_length);
+    if (raw_length == std::size_t(-1)) {
+        last_error = axolotl::ErrorCode::INVALID_BASE64;
+        return std::size_t(-1);
+    }
+    axolotl::decode_base64(input, b64_length, input);
+    return raw_length;
+}
+
+const char * errors[9] {
+    "SUCCESS",
+    "NOT_ENOUGH_RANDOM",
+    "OUTPUT_BUFFER_TOO_SMALL",
+    "BAD_MESSAGE_VERSION",
+    "BAD_MESSAGE_FORMAT",
+    "BAD_MESSAGE_MAC",
+    "BAD_MESSAGE_KEY_ID",
+    "INVALID_BASE64",
+    "BAD_ACCOUNT_KEY",
+};
+
+} // namespace
+
+
+extern "C" {
+
+
+size_t axolotl_error() {
+    return std::size_t(-1);
+}
+
+
+const char * axolotl_account_last_error(
+    AxolotlSession * account
+) {
+    unsigned error = unsigned(from_c(account)->last_error);
+    if (error < 9) {
+        return errors[error];
+    } else {
+        return "UNKNOWN_ERROR";
+    }
+}
+
+
+const char * axolotl_session_last_error(
+    AxolotlSession * session
+) {
+    unsigned error = unsigned(from_c(session)->last_error);
+    if (error < 9) {
+        return errors[error];
+    } else {
+        return "UNKNOWN_ERROR";
+    }
+}
+
+
+size_t axolotl_account_size() {
+    return sizeof(axolotl::Account);
+}
+
+
+size_t axolotl_session_size() {
+    return sizeof(axolotl::Session);
+}
+
+
+AxolotlAccount * axolotl_account(
+    void * memory
+) {
+    return to_c(new(memory) axolotl::Account());
+}
+
+
+AxolotlSession * axolotl_session(
+    void * memory
+) {
+    return to_c(new(memory) axolotl::Session());
+}
+
+
+size_t axolotl_pickle_account_length(
+    AxolotlAccount * account
+) {
+    return enc_output_length(pickle_length(*from_c(account)));
+}
+
+
+size_t axolotl_pickle_session_length(
+    AxolotlSession * session
+) {
+    return enc_output_length(pickle_length(*from_c(session)));
+}
+
+
+size_t axolotl_pickle_account(
+    AxolotlAccount * account,
+    void const * key, size_t key_length,
+    void * pickled, size_t pickled_length
+) {
+    axolotl::Account & object = *from_c(account);
+    std::size_t raw_length = pickle_length(object);
+    if (pickled_length < enc_output_length(raw_length)) {
+        object.last_error = axolotl::ErrorCode::OUTPUT_BUFFER_TOO_SMALL;
+        return size_t(-1);
+    }
+    pickle(enc_output_pos(from_c(pickled), raw_length), object);
+    return enc_output(from_c(key), key_length, from_c(pickled), raw_length);
+}
+
+
+size_t axolotl_pickle_session(
+    AxolotlSession * session,
+    void const * key, size_t key_length,
+    void * pickled, size_t pickled_length
+) {
+    axolotl::Session & object = *from_c(session);
+    std::size_t raw_length = pickle_length(object);
+    if (pickled_length < enc_output_length(raw_length)) {
+        object.last_error = axolotl::ErrorCode::OUTPUT_BUFFER_TOO_SMALL;
+        return size_t(-1);
+    }
+    pickle(enc_output_pos(from_c(pickled), raw_length), object);
+    return enc_output(from_c(key), key_length, from_c(pickled), raw_length);
+}
+
+
+size_t axolotl_unpickle_account(
+    AxolotlAccount * account,
+    void const * key, size_t key_length,
+    void * pickled, size_t pickled_length
+) {
+    axolotl::Account & object = *from_c(account);
+    std::uint8_t * const pos = from_c(pickled);
+    std::size_t raw_length = enc_input(
+        from_c(key), key_length, pos, pickled_length, object.last_error
+    );
+    if (raw_length == std::size_t(-1)) {
+        return std::size_t(-1);
+    }
+    std::uint8_t * const end = pos + raw_length;
+    unpickle(pos, end, object);
+    return pickled_length;
+}
+
+
+size_t axolotl_unpickle_session(
+    AxolotlSession * session,
+    void const * key, size_t key_length,
+    void * pickled, size_t pickled_length
+) {
+    axolotl::Session & object = *from_c(session);
+    std::uint8_t * const pos = from_c(pickled);
+    std::size_t raw_length = enc_input(
+        from_c(key), key_length, pos, pickled_length, object.last_error
+    );
+    if (raw_length == std::size_t(-1)) {
+        return std::size_t(-1);
+    }
+    std::uint8_t * const end = pos + raw_length;
+    unpickle(pos, end, object);
+    return pickled_length;
+}
+
+
+size_t axolotl_create_account_random_length(
+    AxolotlAccount * account
+) {
+    return from_c(account)->new_account_random_length();
+}
+
+
+size_t axolotl_create_account(
+    AxolotlAccount * account,
+    void const * random, size_t random_length
+) {
+    return from_c(account)->new_account(from_c(random), random_length);
+}
+
+namespace {
+
+static const std::size_t OUTPUT_KEY_LENGTH = 2 + 10 + 2 +
+        axolotl::encode_base64_length(32) + 3;
+
+void output_key(
+    axolotl::LocalKey const & key,
+    std::uint8_t sep,
+    std::uint8_t * output
+) {
+    output[0] = sep;
+    output[1] = '[';
+    std::memset(output + 2, ' ', 10);
+    uint32_t value = key.id;
+    uint8_t * number = output + 11;
+    *number = '0' + value % 10;
+    value /= 10;
+    while (value) {
+        *(--number) = '0' + value % 10;
+        value /= 10;
+    }
+    output[12] = ',';
+    output[13] = '"';
+    axolotl::encode_base64(key.key.public_key, 32, output + 14);
+    output[OUTPUT_KEY_LENGTH - 3] = '"';
+    output[OUTPUT_KEY_LENGTH - 2] = ']';
+    output[OUTPUT_KEY_LENGTH - 1] = '\n';
+}
+
+} // namespace
+
+
+size_t axolotl_account_identity_keys_length(
+    AxolotlAccount * account
+) {
+    return OUTPUT_KEY_LENGTH * 2 + 1;
+}
+
+
+size_t axolotl_account_identity_keys(
+    AxolotlAccount * account,
+    void * identity_keys, size_t identity_key_length
+) {
+    std::size_t length = OUTPUT_KEY_LENGTH * 2 + 1;
+    if (identity_key_length < length) {
+        from_c(account)->last_error =
+            axolotl::ErrorCode::OUTPUT_BUFFER_TOO_SMALL;
+        return size_t(-1);
+    }
+    std::uint8_t * output = from_c(identity_keys);
+    output_key(from_c(account)->identity_key, '[', output);
+    output += OUTPUT_KEY_LENGTH;
+    output += OUTPUT_KEY_LENGTH;
+    output[0] = ']';
+    return length;
+}
+
+
+size_t axolotl_account_one_time_keys_length(
+    AxolotlAccount * account
+) {
+    size_t count = from_c(account)->one_time_keys.size();
+    return OUTPUT_KEY_LENGTH * (count + 1) + 1;
+}
+
+
+size_t axolotl_account_one_time_keys(
+    AxolotlAccount * account,
+    void * identity_keys, size_t identity_key_length
+) {
+    std::size_t length = axolotl_account_one_time_keys_length(account);
+    if (identity_key_length < length) {
+        from_c(account)->last_error =
+            axolotl::ErrorCode::OUTPUT_BUFFER_TOO_SMALL;
+        return size_t(-1);
+    }
+    std::uint8_t * output = from_c(identity_keys);
+    output_key(from_c(account)->last_resort_one_time_key, '[', output);
+    output += OUTPUT_KEY_LENGTH;
+    for (auto const & key : from_c(account)->one_time_keys) {
+        output_key(key, ',', output);
+        output += OUTPUT_KEY_LENGTH;
+    }
+    output[0] = ']';
+    return length;
+}
+
+
+size_t axolotl_create_outbound_session(
+    AxolotlSession * session,
+    AxolotlAccount * account,
+    void const * their_identity_key, size_t their_identity_key_length,
+    unsigned their_one_time_key_id,
+    void const * their_one_time_key, size_t their_one_time_key_length,
+    void const * random, size_t random_length
+) {
+    if (axolotl::decode_base64_length(their_identity_key_length) != 32
+            || axolotl::decode_base64_length(their_one_time_key_length) != 32
+    ) {
+        from_c(session)->last_error = axolotl::ErrorCode::INVALID_BASE64;
+        return std::size_t(-1);
+    }
+    axolotl::Curve25519PublicKey identity_key;
+    axolotl::RemoteKey one_time_key;
+
+    axolotl::decode_base64(
+        from_c(their_identity_key), their_identity_key_length,
+        identity_key.public_key
+    );
+    one_time_key.id = their_one_time_key_id;
+    axolotl::decode_base64(
+        from_c(their_one_time_key), their_one_time_key_length,
+        one_time_key.key.public_key
+    );
+
+    return from_c(session)->new_outbound_session(
+        *from_c(account), identity_key, one_time_key,
+        from_c(random), random_length
+    );
+}
+
+
+size_t axolotl_create_inbound_session(
+    AxolotlSession * session,
+    AxolotlAccount * account,
+    void * one_time_key_message, size_t message_length
+) {
+    std::size_t raw_length = b64_input(
+        from_c(one_time_key_message), message_length, from_c(session)->last_error
+    );
+    if (raw_length == std::size_t(-1)) {
+        return std::size_t(-1);
+    }
+    return from_c(session)->new_inbound_session(
+        *from_c(account), from_c(one_time_key_message), raw_length
+    );
+}
+
+
+size_t axolotl_matches_inbound_session(
+    AxolotlSession * session,
+    void * one_time_key_message, size_t message_length
+) {
+    std::size_t raw_length = b64_input(
+        from_c(one_time_key_message), message_length, from_c(session)->last_error
+    );
+    if (raw_length == std::size_t(-1)) {
+        return std::size_t(-1);
+    }
+    bool matches = from_c(session)->matches_inbound_session(
+        from_c(one_time_key_message), raw_length
+    );
+    return matches ? 1 : 0;